Department of Biochemistry and Molecular Biology, Hajee Mohammad Danesh Science and Technology University, Dinajpur, Bangladesh.
Advanced Molecular Lab, Department of Microbiology, President Abdul Hamid Medical College, Karimganj-2310, Kishoreganj, Bangladesh; COVID-19 Diagnostic Lab, Department of Microbiology, Noakhali Science and Technology University, Noakhali 3814, Bangladesh.
Sci Total Environ. 2023 Dec 15;904:166704. doi: 10.1016/j.scitotenv.2023.166704. Epub 2023 Aug 30.
Application of greener pretreatment technology using robust ligninolytic bacteria for short duration to deconstruct rice straw and enhance bioethanol production is currently lacking. The objective of this study is to characterize three bacterial strains isolated from the milieux of cow rumen and forest soil and explore their capabilities of breaking down lignocellulose - an essential process in bioethanol production. Using biochemical and genomic analyses these strains were identified as Bacillus sp. HSTU-bmb18, Bacillus sp. HSTU-bmb19, and Citrobacter sp. HSTU-bmb20. Genomic analysis of the strains unveiled validated model hemicellulases, multicopper oxidases, and pectate lyases. These enzymes exhibited interactions with distinct lignocellulose substrates, further affirmed by their stability in molecular dynamic simulations. A comprehensive expression of ligninolytic pathways, including β-ketoadipate, phenyl acetate, and benzoate, was observed within the HSTU-bmb20 genome. The strains secreted approximately 75-82 U/mL of cellulase, xylase, pectinase, and lignin peroxidase. FT-IR analysis of the bacterial treated rice straw fibers revealed that the intensity of lignin-related peaks decreased, while cellulose-related peaks sharpened. The values of crystallinity index for the untreated control and the treated rice straw with either HSTU-bmb18, or HSTU-bmb19, or HSTU-bmb20 were recorded to be 34.48, 28.49, 29.36, 31.75, respectively, which are much higher than that of 13.53 noted for those treated with the bacterial consortium. The ratio of fermentable cellulose in rice straw increased by 1.25-, 1.79-, 1.93- and 2.17-fold following treatments with HSTU-bmb18, HSTU-bmb20, HSTU-bmb19, and a mixed consortium of these three strains, respectively. These aggregative results suggested a novel model for rice straw deconstruction utilizing hydrolytic enzymes of the consortium, revealing superior efficacy compared to individual strains, and advancing cost-effective, affordable, and sustainable green technology.
目前，缺乏使用稳健木质素分解菌的绿色预处理技术在短时间内对水稻秸秆进行解构并提高生物乙醇产量的应用。本研究的目的是对从牛瘤胃和森林土壤环境中分离出的三株细菌进行特征描述，并探索它们分解木质纤维素的能力——这是生物乙醇生产的一个关键过程。通过生化和基因组分析，这些菌株被鉴定为芽孢杆菌 HSTU-bmb18、芽孢杆菌 HSTU-bmb19 和柠檬酸杆菌 HSTU-bmb20。对这些菌株的基因组分析揭示了有效的半纤维素酶、多铜氧化酶和果胶裂解酶模型。这些酶与不同的木质纤维素底物相互作用，进一步通过分子动力学模拟得到证实。在 HSTU-bmb20 基因组中观察到完整的木质素分解途径，包括β-酮戊二酸、苯乙酸和苯甲酸。这些菌株分泌约 75-82 U/mL 的纤维素酶、木聚糖酶、果胶酶和木质素过氧化物酶。对细菌处理过的水稻秸秆纤维进行傅里叶变换红外（FT-IR）分析显示，木质素相关峰的强度降低，而纤维素相关峰变得尖锐。未经处理的对照和用 HSTU-bmb18、HSTU-bmb19 或 HSTU-bmb20 处理的水稻秸秆的结晶度指数值分别记录为 34.48、28.49、29.36 和 31.75，明显高于用细菌混合物处理的那些的 13.53。水稻秸秆中可发酵纤维素的比例分别提高了 1.25 倍、1.79 倍、1.93 倍和 2.17 倍，用 HSTU-bmb18、HSTU-bmb20、HSTU-bmb19 和三种菌株的混合菌处理后。这些综合结果提出了一种利用该混合物的水解酶对水稻秸秆进行解构的新模型，与单个菌株相比表现出更好的效果，并推进了经济高效、负担得起且可持续的绿色技术。
